Premiere export sound problem

I can't for the life of me seem to get an export of a project to play back with the sound keyed right. It keeps coming out like a 1/2 sec. or so off so all my edits are off and it's quite annoying. I've been exporting to h.264 in Media Encoder trying to get the settings as high quality as possible while under 500 mb... which shouldnt be that hard for 5 minutes of video. Trying to export it right now as a straight up uncompressed avi to see if that fixes it but we'll see. It plays back right in the timeline... just can't get the full exported video right. Thanks.